The solution viscosity and viscosity stability of the polymer used for tertiary oil recovery are important indicators to determine its using effect. Reservoir temperature, mineralization degree of formation water and injection water affect the viscosifying capacity of the polymer solution directly. For partially hydrolyzed polyacrylamide, although it has obvious viscosifying action in fresh water, the hydrodynamic radius of polymer macromolecules decreases with the increase of reservoir temperature, mineralization degree of formation water and injection water, in the meantime, the increase of the adsorption amount of this polymer on the surface of rocks also decreases the valid concentration of the solution, resulting in a decline of the solution viscosity. Amphiphilic macromolecules are an important class of water-soluble polymers; by introducing a small amount of hydrophobic groups on the hydrophilic macromolecular chains, an intramolecular or intermolecular hydrophobic interaction is generated, rendering the macromolecules to form a steric network structure, and thus has a remarkable viscosifying effect. By increasing the hydrophobic group content on the macromolecule chain or increasing the molecular weight, the impacts of high temperature and high salinity can be resisted to some extent; however, it may also result in deterioration of dissolving capacity of the polymer, substantial increase of dissolving time, easy shear degradation of the macromolecular chain and easy adsorption on the rock and other problems. Furthermore, with the increase of formation temperature and water mineralization degree, these problems are particularly serious.
Heavy oil resource has become one of the important natural resources for strategic replacement, but it's difficult to exploit. The main reason is that the heavy oil is high in viscosity, high in gum, asphaltenes contents or wax content, and does not easily flow in formation, wellbore and pipeline. Additionally, because of the great oil-water mobility ratio, it will also cause fast water breakthrough, high water content, and easy formation sand production and other serious problems negatively affecting the oil production.
Nowadays, to keep the viscosifying properties and viscosity stability of the polymer solution, and to improve its ability for heavy oil emulsification, dispersion and viscosity-reduction have great significance on the enhancementof crude oil recovery and the maximizing of tapping of the potential underground residual crude oil.